FIG. 3 is a block diagram showing a configuration of a conventional induction heating apparatus, for example, disclosed in Patent Literature 1. The induction heating apparatus of FIG. 3 performs duty control in which, when two inverter circuits simultaneously operate for heating, the inverter circuits are controlled to alternate between a high heating power mode and a low heating power mode in predetermined cycles. Referring to FIG. 3, the conventional induction heating apparatus is provided with: a rectifier circuit 102 rectifying alternating-current power from an alternating-current power supply 101; a first inverter circuit 104 converting output power from the rectifier circuit 102, to high-frequency power, and supplying a current to a first heating coil 106; a second inverter circuit 105 converting output power from the rectifier circuit 102, to high-frequency power, and supplying a current to a second heating coil 107; current detection means 103 for detecting an input current from the alternating-current power supply 101; and control means 108 for controlling the durations of ON periods of a plurality of semiconductor switches in the first inverter circuit 104 and the second inverter circuit 105 according to the detection result obtained by the current detection means 103.
In this case, after an input current to one of the first inverter circuit 104 and the second inverter circuit 105 reaches a target value, the control means 108 makes the one inverter circuit and the other inverter circuit operational simultaneously. In addition, when the first and second inverter circuits 104 and 105 operates simultaneously, at least one of the inverter circuits performs duty control including ON periods and OFF periods. Therefore, even when the two inverter circuits 104 and 105 share the rectifier circuit 102 and the current detection means 103, it is possible to supply an amount of power to each of the first inverter circuit 104 and the second inverter circuit 105. In addition, since an input current can be detected accurately, it is possible to accurately supply an amount of power to each of the inverter circuits 104 and 105.
Patent Literature 1: Japanese Patent laid-open Publication No. 2010-212052 A